Rotating machines, such as pumps and compressors, display operating characteristics which come in part from the bearing parameters. With the use of magnetic bearings, these parameters may be controlled or modified as the rotor is stationary or turning. In general, conventional fluid film bearings or so-called anti-friction bearings cannot be adjusted or modified either when the rotor is stationary nor when it is turning in the bearings. So magnetic bearings offer many advantages over the more conventional bearings.
Machinery characteristics come in part from the balance of the rotors; but even when a rotor is brought into perfect balance, other dynamic characteristics may still produce undesirable running characteristics. These latter characteristics stem from the dynamics of the system which may be described in terms of the masses and their distributions, damping properties of the materials of construction and configurations of the design, and the stiffnesses of the various components and their interactions. Included in these above noted parameters are the bearings that support the rotating elements, which taken together may be simply called the rotor.
By varying the defining parameters of the bearings, the overall system dynamics may be controlled. With magnetic bearings, these parameters may be adjusted or changed when the rotors are running; (i.e., turning within the bearings) or even when they are in support, but not turning. It is important to understand that support is not usually attained in a fluid film bearing until the rotor is turning. Such is not the case with the magnetic bearing. It may be in support whether the rotor is turning or not.
Many special features may be designed into a magnetic bearing. It is some of the unique features that are addressed in this invention, including the isolation or "canning", the support system, special speed dependent parameters, special controls for hybrid bearings, and balancing without turning of the rotor.